1. Field:
This invention relates to a gas-actuated autoloading firearm, such as a semiautomatic shotgun, of the type wherein firing gases are tapped from near the muzzle end of the barrel into a tubular magazine below the barrel. More particularly, the invention relates to a novel piston and obturator assembly for use in the magazine of such a firearm.
2. State of the Art:
In a typical autoloading shotgun of the gas-actuated type, a tubular magazine for housing cartridges is mounted below and parallel to the barrel of the shotgun, and firing gases are tapped from the barrel into the magazine. The gases actuate reloading mechanism associated with the magazine tube. Usually the end of this magazine which is near the muzzle of the barrel is supported by a barrel ring, and the firing gases are tapped through a channel which is formed in the barrel ring into an annular cylinder surrounding the magazine. The tapped gases then press against the face of an annular piston which is slidably disposed in the annular cylinder. The piston is thus driven towards the breech of the shotgun. The motion of the annular piston is coupled to further mechanism to expel the spent cartridge from the breech while loading another shell thereinto in position for firing. One problem with such arrangements is that the firing gases often carry solid particles such as powder into the cylinder. Such particles may build upon the wall of the cylinder causing the piston to drag or stick. This buildup also tends to make it difficult to remove the piston and associated parts from the front of the magazine tube.